The present invention relates to liquid cooling systems, and more particularly to an improved method and apparatus for use in post-mix cold beverage dispensers in which measured quantities of fluids such as carbonated water and flavored syrups are selectively mixed and discharged through manually actuated dispensing heads.
Commercial installations of post-mix beverage dispensers typically include a "tower" with dispensing heads conveniently positioned on a foodservice counter for selectively mixing and discharging a variety of flavored syrups with plain or carbonated water. Due to the narrow front-to-back depth of the counter, severe design and space limitations are placed on the tower configuration which often preclude installation of a conventional refrigerating unit or cooler in the immediate vicinity of the dispensing heads. Consequently, the tower is installed on the counter with chilled water delivered through a long conduit from a remotely located cooler.
It is important for consistent performance of a cold beverage dispenser to deliver beverages at the same chill temperature each time. Under frequent usage, the temperature of the ingredients at the dispensing heads can be maintained fairly constant thus assuring a pleasing chilled beverage each time without excessive foaming. However, for so-called "casual" drinks where the dispenser may be idle for a prolonged period of time, usually 15 minutes or more, heat gain from the surroundings tends to increase the temperature of the stagnant ingredient near the dispensing heads. The temperature increase in the resulting beverage will vary depending on the quantity of quiescent water and syrup in the conduit and on the duration of exposure.
Several approaches for alleviating this problem are in use. One, such as disclosed in U.S. Pat. No. 4,969,576 to Merrill et al, periodically draws off an amount of warmed-up water near the dispensing heads allowing it to be replaced with chilled water from an ice-chilled cast aluminum plate. Another approach, disclosed in U.S. Pat. No. 4,781,309 to Vogel, recirculates the chilled water at a regulated temperature between a remote cooler and the dispensing heads in the tower. Both of these approaches provide an immediate discharge on demand of chilled water regardless of the length of conduit or the time elapsed since the dispenser was last used, but it does not compensate for increases in syrup temperature due to heat gain from external sources. Some installations, therefore, also chill the various flavored syrups by passing them through a cast aluminum heat exchanger with the chilled water, such as disclosed in U.S. Pat. No. 4,781,309 supra, or by running the syrup in lines along side the chilled water line within the insulated conduit.
After the syrup lines reach the beverage tower, however, they separate from the water line and continue to their respective dispensing heads for mixing and discharging with the water. When there is no demand, the quiescent syrup will warm up where the lines are separated resulting in a higher beverage temperature depending on the quantity of quiescent ingredients and the time lapse between usages.